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First of all what kind of moment exhibits the photon under its propagation to spacetime continium -quadrupole,dipole or monopole! Please, explain me- why. Do Give some arguements! When it propagetes does it exegerate gravitatinal waves? Why only quadrupoles do that ?

Qmechanic
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Коцето Райчев
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1 Answers1

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Because gravity is a tensor field, and the lowest excitation is quadrupole. For a vector field it would be a dipole; and for a scalar field it is what you have termed a monopole: like a frog croaking, or the fundamental mode of a drum, it just goes all in, and all out.

The terminology derives from the terms of a multipole series expansion, ususally first studied in electromagnetic field theory, or a course in mathematical physics.

Peter Diehr
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  • Yes ,it merges from my previous question? And as in my previous ,in this one I still litteraly don't have any exact answer. Does photon creates create GW in its propagation. Can it have quadrupole moment? Why, so ? – Коцето Райчев Mar 01 '16 at 20:10
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    The photon is a vector particle, as it originates in the vector electromagnetic field. So no, a photon could not create a gravitational wave. Of course, you can make a quadrupole field from two dipoles: you can do this with two magnets. So under the proper conditions you could generate a gravitational wave with two photons, in the proper configuration - they would have to exist in the region to be disturbed simultaneously, and would have to cross at an angle. Consider how LIGO works: if it can detect, it may also be able to generate - but at an impossibly low level, impossible to detec. – Peter Diehr Mar 01 '16 at 23:20
  • Would you please explain why the way is impossible for detection? But please no answers like the field is negligible or the filed is mega turbo giga small . Negligible or very very very small does not make any sense for me . Only values make it ! – Коцето Райчев Mar 03 '16 at 22:57